1. Field of the Invention
The present invention relates generally to an image sensor and a method of manufacturing the same, and more particularly to a CMOS image sensor and a method of manufacturing the same.
2. Description of the Related Art
An image sensor converts an optical image to electrical signals. With the continued development of the computer and communication industries, the demand for image sensors has rapidly increased as devices including digital cameras, camcorders, security cameras, and micro-cameras for medical purposes employ image sensors.
A CMOS image sensor offers operation ease, and can be implemented using various scanning methods. Furthermore, signal processing circuits can be integrated into a single chip, thereby enabling a product to be miniaturized, and compatible CMOS processing technology can be used, thereby reducing the manufacturing cost. Power consumption is also low; therefore such sensors can be applied to products where battery capacity is limited.
As described above, the CMOS image sensor is generally manufactured using CMOS processing technology, and aluminum, which is widely used in the CMOS processing, has been used as the metal wires that interconnect the various elements of the CMOS image sensor. However, aluminum wires have a high sheet resistance value, and, therefore, they must be formed to a greater thickness than copper wires to achieve similar performance. Accordingly, the interlayer dielectric in which the aluminum wires are formed must also be thicker relative to a comparable interlayer dielectric in which copper wires are formed using a dual damascene process.
When aluminum interconnecting wires are used as described above, the vertical distance from a photoelectric conversion element, formed in a substrate, to an uppermost micro-lens at a top of the structure is great, so that the optical path along which light photons travel from the an external source to the photoelectric conversion element is likewise great, thereby reducing the sensitivity of the photoelectric conversion element.
In order to address the above problem, research has been conducted on the application of copper wires. However, the use of copper wires carries with it an enormous investment in fabrication equipment.